The format to set storage class environment variables is as follows

`MINIO_STORAGE_CLASS_STANDARD=EC:parity`
`MINIO_STORAGE_CLASS_RRS=EC:parity`

For example, set `MINIO_STORAGE_CLASS_RRS` parity 2 and `MINIO_STORAGE_CLASS_STANDARD` parity 3

```sh
export MINIO_STORAGE_CLASS_STANDARD=EC:3
export MINIO_STORAGE_CLASS_RRS=EC:2
```

const (
	ClassStandard = "standard"
	ClassRRS      = "rrs"
	Optimize      = "optimize"
	InlineBlock   = "inline_block"

	// Reduced redundancy storage class environment variable
	RRSEnv = "MINIO_STORAGE_CLASS_RRS"
	// Standard storage class environment variable
	StandardEnv = "MINIO_STORAGE_CLASS_STANDARD"
	// Optimize storage class environment variable
	OptimizeEnv = "MINIO_STORAGE_CLASS_OPTIMIZE"

	tests := []struct {
		sc   string
		want bool
	}{
		{"STANDARD", true},
		{"REDUCED_REDUNDANCY", true},
		{"", false},
		{"INVALID", false},
		{"123", false},
		{"MINIO_STORAGE_CLASS_RRS", false},
		{"MINIO_STORAGE_CLASS_STANDARD", false},
	}
	for i, tt := range tests {
		if got := IsValid(tt.sc); got != tt.want {
			t.Errorf("Test %d, Expected Storage Class to be %t, got %t", i+1, tt.want, got)

MINIO_STORAGE_CLASS_RRS: Format "EC:<Default_Parity_Reduced_Redundancy_Class>" (e.g. "EC:3"). This sets the number of parity drives for MinIO server in Reduced Redundancy mode. Objects are stored in Reduced Redundancy mode, if Put request specifies RRS storage class...

or environment variables

```
KEY:
storage_class  define object level redundancy

ARGS:
MINIO_STORAGE_CLASS_STANDARD  (string)    set the parity count for default standard storage class e.g. "EC:4"
MINIO_STORAGE_CLASS_RRS       (string)    set the parity count for reduced redundancy storage class e.g. "EC:2"
MINIO_STORAGE_CLASS_COMMENT   (sentence)  optionally add a comment to this setting
```

#### Etcd